Conventional methods for inhibiting corrosion (rust formation) of iron and steel materials include a coating method in which contact with oxygen, sulfides, halides, and the like is prevented by a surface coating composed of a paint or other organic materials, a zinc plating method in which the processing object is dipped for a certain time into molten zinc and the zinc is caused to adhere thereto, and a metal spraying method in which zinc and aluminum are melted and caused to adhere as a composite film to the surface of an iron or steel structure and the oxidation with time is suppressed and endurance is improved correspondingly to the thickness of the formed coating by using the sacrificial anode reaction.
The following problems were associated with the above-described corrosion protection methods that have been conventionally implemented. Thus, in the coating method, because the organic solvent coating was used, hardness was insufficient, the function of shielding the metal surface form air was degraded due to surface damage or wear-induced defects, and corrosion occurred as a result of weathering, UV degradation, outer damage and the like.
With the zinc plating method, corrosion protection performance could be demonstrated for about 10 years, but a large plant suitable for dipping was required to implement the method and the method could not be adapted to maintain the existing iron and steel structures. Furthermore, it could not be employed with thin steel sheets and long steel materials due to problems associated with melting temperature and dipping pool. In recent years, the establishment of technology for zinc-aluminum alloy plating has been advanced, but the cost of equipment such as ceramic furnaces was high and cost efficiency of the process created a problem. Moreover, in the zinc-aluminum alloy plating, the size of aluminum crystal grains differed due to a difference in the cooling rate of zinc and aluminum. The resultant problem associated with characteristics was that the so-called grain boundary corrosion could easily occur.
The metal spraying method demonstrated a level of protection higher than that attained with zinc plating because the metal of internal zones was protected by a sacrificial anode reaction. However, mechanical equipment for metal spraying (spraying gun, power source unit, air blowing unit, wire coiling-uncoiling unit, spray extension cord, and the like) was required. Furthermore, the process efficiency was also dependent on the technological skills of the operator, and at a daily processing surface area of about 30 m2, transportation and preparation of equipment placed a large load on the operator, thereby creating the necessity to examine the profitability of the process. Yet another problem was that spraying on the already installed structures and processing of narrow structural components were difficult. Moreover, in order to cause forcible adhesion of molten zinc and aluminum to the surface of the processing object, the surface of iron and steel structures had to be pretreated by shot blasting or with a surface roughening agent so that the anchor effect be demonstrated.
Accordingly, it is an object of present invention to provide a rust inhibitor which is capable of resolving the above-described problems, while realizing the advantages of the conventional methods for corrosion protection, that is, a rust inhibitor which ensures the simplicity of application typical for a coating process and can demonstrate excellent characteristics similar to those obtained with a metal spraying method.